给定以下具有两个多对多关系的模型:
class Child(models.Model):
name = models.CharField(max_length=80)
class Foo(models.Model):
bar = models.ManyToManyField(Child)
baz = models.ManyToManyField(Child)
这将产生以下错误:
accounts.foo: Accessor for m2m field 'bar' clashes with related m2m field 'Child.foo_set'. Add a related_name argument to the definition for 'bar'.
accounts.foo: Accessor for m2m field 'baz' clashes with related m2m field 'Child.foo_set'. Add a related_name argument to the definition for 'baz'.
很好;我不需要反向关系。According to the Django docs for related_name (据我所知只在ForeignKey下),我可以设置related_name="+"
,不会创建向后关系:
class Child(models.Model):
name = models.CharField(max_length=80)
class Foo(models.Model):
bar = models.ManyToManyField(Child, related_name="+")
baz = models.ManyToManyField(Child, related_name="+")
但这不起作用:
accounts.foo: Accessor for m2m field 'bar' clashes with related m2m field 'Child.+'. Add a related_name argument to the definition for 'bar'.
accounts.foo: Reverse query name for m2m field 'bar' clashes with related m2m field 'Child.+'. Add a related_name argument to the definition for 'bar'.
accounts.foo: Accessor for m2m field 'baz' clashes with related m2m field 'Child.+'. Add a related_name argument to the definition for 'baz'.
accounts.foo: Reverse query name for m2m field 'baz' clashes with related m2m field 'Child.+'. Add a related_name argument to the definition for 'baz'.
我需要做些什么来避免创建反向关系?
发布于 2012-12-18 01:41:30
我认为你只需要给这两个字段不同的related_names:
class Child(models.Model):
name = models.CharField(max_length=80)
class Foo(models.Model):
bar = models.ManyToManyField(Child, related_name="bar")
baz = models.ManyToManyField(Child, related_name="baz")
如果您没有给出相关的名称,那么它将尝试在Child
模型上创建两次相同的访问器名称(foo_set
)。如果您提供相同的相关名称,它将再次尝试创建相同的访问器两次,因此您需要提供唯一的相关名称。使用上面的代码定义模型,然后给定一个Child
实例c
,您就可以使用c.bar.all()
和c.baz.all()
访问相关的Foo
对象。
如果您不想要向后关系,那么将一个+
附加到每个(唯一的)相关名称:
class Foo(models.Model):
bar = models.ManyToManyField(Child, related_name="bar+")
baz = models.ManyToManyField(Child, related_name="baz+")
https://stackoverflow.com/questions/13918968
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